RWTPCValQueueGuarded< Type > Class Template Reference
[Interthread Communication]

First-in-first-out (FIFO) queue that provides producer-consumer synchronization semantics for exchanging guarded values between cooperating threads. More...

#include <rw/itc/RWTPCValQueueGuarded.h>

Inheritance diagram for RWTPCValQueueGuarded< Type >:

List of all members.

Public Member Functions
	RWTPCValQueueGuarded (size_t maxCapacity=0, bool isOpen=true)
	~RWTPCValQueueGuarded (void)

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Detailed Description

template<class Type>
class RWTPCValQueueGuarded< Type >

RWTPCValQueueGuarded<Type> is a first-in-first-out (FIFO) queue that provides producer-consumer synchronization semantics for exchanging guarded values between cooperating threads.

In the producer-consumer synchronization model, reader threads (consumers) are blocked while the queue is empty, and writer threads (producers) are blocked while the queue is full. The queue is considered full when the number of unread entries equals or exceeds some user-specified maximum capacity.

The write operations inherited by this class bind a guard functor to each value prior to storing that value in an internal buffer. A guard functor is used during read operations to determine whether the associated value is currently eligible for retrieval from the buffer.

Examples

 #include <rw/itc/RWTPCValQueueGuarded.h>
 #include <rw/thread/RWThreadFunction.h>  // for RWThreadFunction
 #include <rw/functor/functorR0.h>        // for RWTFunctorR0<>
 #include <iostream.h>
 
 enum Command { RUN, STOP, PROCESS, EXIT };
 RWTPCValQueueGuarded<Command>  pcQueue;
 bool isRunning = false;
 
 // The guard function
 bool canProcess() { return isRunning; }
 
 void reader(void)
 {
    // Get commands from queue, update state, and write to stdout
    Command command;
    while (EXIT != (command = pcQueue.read())) {
      switch(command) {
        case RUN: cout<<"RUN"<< endl; isRunning=true; break;
        case STOP: cout<<"STOP"<<endl; isRunning=false; break;
        case PROCESS: cout<<"PROCESS"<<endl; break;
      }
    }
    cout<<"EXIT"<<endl;
 }
      
 int main()
 {
    RWThread thread = rwtMakeThreadFunctionG(void,reader);
    RWTFunctorR0<bool> guard =
              rwtMakeFunctorR0G(bool,bool,canProcess);
 
    thread.start();
    pcQueue.write(PROCESS,guard);  // PROCESS commands initially
    pcQueue.write(PROCESS,guard);  // blocked by guards...
    pcQueue.write(PROCESS,guard);
    pcQueue.write(RUN);            // Until the state is changed
    pcQueue.write(PROCESS,guard);  // These won't block...
    pcQueue.write(PROCESS,guard);
    pcQueue.write(PROCESS,guard);
    pcQueue.write(STOP);          // Start blocking PROCESS again
    pcQueue.write(PROCESS,guard); // These get blocked...
    pcQueue.write(PROCESS,guard);
    pcQueue.write(PROCESS,guard);
    pcQueue.write(RUN);           // Let the reader read the rest
    pcQueue.write(EXIT);
    thread.join();
    return 0;
 }

* This code produces the following output:

 RUN
 PROCESS
 PROCESS
 PROCESS
 PROCESS
 PROCESS
 PROCESS
 STOP
 RUN
 PROCESS
 PROCESS
 PROCESS
 EXIT

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Constructor & Destructor Documentation

template<class Type >

RWTPCValQueueGuarded< Type >::RWTPCValQueueGuarded	(	size_t	maxCapacity = 0,
		bool	isOpen = true
	)			[inline]

Constructs a value-based, guarded, producer-consumer queue instance.

The parameter maxCapacity specifies the maximum number of unread entries allowed to accumulate within the queue. Once the number of entries in the queue equals this number, any thread attempting to write an additional entry is blocked until an entry is removed by a RWTPCValBufferBaseGuarded::read() operation, or until the capacity is increased. A capacity of zero, the default, indicates that the queue has no size limit, except as imposed by memory limitations, and that all RWTPCValBufferBaseGuarded::write() operations should complete without blocking.

The parameter isOpen is a bool value that specifies whether the queue should be initialized in the open state, true, the default, or the closed state, false.

template<class Type >

RWTPCValQueueGuarded< Type >::~RWTPCValQueueGuarded

(

void

)

[inline]

Destructor.